The invention is based on an engine hood for motor vehicles, which is provided with a deformable head impact zone to protect pedestrians in the event of a collision with the motor vehicle, as is known, for example, from EP 1 093 980 A1.
In the event of a pedestrian colliding with a vehicle, in particular in the event of a head-on impact, the upper body or head of the pedestrian often strikes the engine hood of the vehicle, which can cause serious injury to the pedestrian. To reduce this risk of injury, the region of potential impact of the pedestrian on the engine hood has to be as yielding and deformable as possible. However, there is only a very small amount of free space available between the engine hood and the equipment below it, and consequently the deformation movement by which the engine hood can yield in the event of a collision with a pedestrian is only very small. Furthermore, to protect the occupants of the vehicle in the event of a head-on collision, the engine hood has to satisfy requirements relating to component rigidity and has to be configured in such a way that defined deformation and therefore a controlled conversion of energy occur in the event of the engine hood crumpling in the longitudinal direction of the vehicle.
To satisfy these contradictory demands, the engine hood is in many cases configured as an assembly of an outer shell (which forms the body paneling) and a reinforcing shell, which is arranged below the outer shell and is provided with suitable deformation and stiffening elements. The generic EP 1 093 980 A1 has disclosed, for example, an engine hood with an outer shell and a reinforcing shell, the flexural rigidity of which varies over the engine hood in such a way that the engine hood has a relatively high flexural rigidity in the center but a lower flexural rigidity in the edge regions. This design is intended to ensure that in the event of a central head impact, the entire mass of the engine hood counteracts the impact, whereas in the event of a head impact in the edge regions, the energy of the head impact is dissipated over a small part of the engine hood. The design of the engine hood which is known from EP 1 093 980 A1 therefore aims to achieve an approximately constant deformation of the engine hood irrespective of the impact site.
However, current knowledge has shown that when assessing the effects of a collision of a pedestrian with the engine hood, it is not only the bending of the engine hood but also, to a much greater extent, the acceleration or deceleration of the impacting body, i.e. the forces acting on the body, which play an important role. In addition, as before, the maximum possible free space has to be available between engine hood and the equipment below it, so that in the event of a collision with a pedestrian, the engine hood can yield by the largest possible deformation movement before it comes into contact with the (generally very hard) equipment below it.